The present invention relates, in general, to the manufacture of prescription eyeglass lenses and, more particularly, to a unique method and apparatus for accurately and rapidly manufacturing such lenses to prescription through the assembly of modular components. The invention further relates to a method and apparatus for identifying and assembling component parts of a prescription lens and incorporates a method of edging lenses to fit selected frames for complete eyeglass manufacture.
For over 100 years, the ophthalmic lens manufacturing industry has remained static with eyeglass lenses being produced, using grinding and polishing technology that has been available for most of that period. Although some new lens materials have been introduced, such as plastics, and although a small percentage of prescription lenses can be cast with the finished optics, the vast majority of both glass and plastic lenses must still be ground and polished, one at a time. This process involves so many manufacturing steps that human error remains a large cost of doing business.
Many attempts have been made to modernize the ophthalmic lens industry, but the many failures are testimony to the fact that the production of quality eyeglass optics is far more complicated than is generally imagined. There are so many different prescriptions possible that most technological innovations simply do not take into account all of the possibilities, and thus are unacceptable.
One change that was made many years ago involved a shifting of the lens manufacturing and lens edging steps away from the retail optometrist to wholesale laboratories which are geared to large volume production of prescription lenses. This shift was based almost solely on ecomonics, since the cost of lens manufacturing equipment and inventory was so great that it was beyond the reach of most retail operations that wished to remain price-competitive. However, in giving up the manufacturing postion of the business, the retail lens dispenser also gave up many desirable features of his business, such as speed in meeting customer requirements and detailed product control. Problems in communication to and from the wholesaler, slow delivery times, the cost of double record keeping, the cost of double overhead and the inflexibility of a wholesale manufacturing operation were but a few of the problems created by this shift. The problems encountered by wholesale manufacturers in meeting the needs of the lens dispensers spurred the creation of "semi-finished" lens blank manufacturers who supplied semi-finished blanks to the wholesalers, creating yet another level of lost control and increased inventory variability. This additional level in the process of supplying lenses further compounded the problems noted above since such manufacturers proceeded to expand the availability of semifinished lens blanks, increasing the wholesalers inventory record keeping problems, and creating additional complexities and costs.
Eyeglass frame manufacturers contribute to the problems which exist in the industry since frame shapes and sizes are now dictated largely by fashion, and thus are subject to constant change. Since the frame geometry, or shape, always dictates the optical configuration of the prescription lens, such geometry is a critical variable that must be precisely defined before the lenses are produced. However, the huge number of frame shapes now available on the market cannot be managed efficiently by even the largest wholesale laboratories.
The present procedure for obtaining a pair of prescription eyeglasses requires that the patient first have his or her eyes examined and corrective lenses prescribed. An optician at the retail dispensary level helps the patient select a suitable frame that is compatible with the prescribed lenses and the distance between the patient's eyes is measured so that the distance between the major reference points of the lenses, when they are placed in the frames, will match the line of sight of the patient's eyes. The optical prescription as well as data relating to the style, size and shape of the frame is communicated to a wholesale laboratory where the lenses are to be manufactured. In a small portion of cases, the prescription can be produced from stock lenses often present at the dispenser's location, but most prescriptions must be surfaced from a blank. The prescription is verified by the wholesale laboratory and optical computations are made to select the proper lens blanks for the patient and for the selected frame so that the required frame shape can be "cut out" from the surfaced blanks. The lens blanks are then pulled from inventory and are mounted on blocks, or holders, which enable the blanks to be mounted in lens grinding and polishing equipment. A grinding and polishing tool, premanufactured to the compound curves required by the particular prescription, is selected from inventory. This tool holds the abrasive and polishing pads required to surface the lense through oscillation on the surface of the lens blank to contour the lens surface to the final compound curve geometry required by the prescription. A number of steps are required, using finer and finer abrasives, to produce the required high luster optical finish. This grinding and polishing process is ordinarily done so as to properly relocate the optical center of the lens from its geometric center to an offset location which corresponds to the patient's line of sight through the frame. This grinding to produce not only a prescription but decentration of the optical center requires complex calculations and is a significant source of error. Further, such grinding operation introduces distortions in the lens, which is often a source of customer dissatisfaction.
Once the lens has been polished, it is optically measured for correctness and then undergoes an edging process where the lens is geometrically edge-shaped to fit the frame selected by the patient. This requires an accurate location of the optical center of each lens of a pair with respect to the frame so that the resultant lenses, when mounted, will fit the patient. The completed spectacles are then optically and cosmetically inspected and shipped to the dispenser. The dispenser confirms the accuracy of the completed prescription and recalls the patient for fitting and delivery.
The normal process described above takes several days to complete, even if all of the necessary components are readily available at the laboratory. If a lens blank or particular frame is not available, additional delays--while the needed component is obtained from a manufacturer--are encountered. Because of the reciprocal relationship between a dispenser and a wholesale laboratory, there is a great redundancy in record keeping. Furthermore, the time required for this process is objectionable to everyone, particularly the patient, and all of the handling and record keeping required is costly and inconvenient. Furthermore, the potential for miscommunication is great and may result in conflict between the dispenser/retailer and the wholesaler, or between the dispenser/retailer and the patient, often leading to a loss of customers.